Subject: [PATCH 03/18] asm/rwonce: Allow __READ_ONCE to be overridden by the architecture

From: Will Deacon <[email-masked]>
Date: Tue, 30 Jun 2020 18:37:19 +0100

The meat and potatoes of READ_ONCE() is defined by the __READ_ONCE()
macro, which uses a volatile casts in an attempt to avoid tearing of
byte, halfword, word and double-word accesses. Allow this to be
overridden by the architecture code in the case that things like memory
barriers are also required.

Acked-by: Paul E. McKenney <[email-masked]>
Signed-off-by: Will Deacon <[email-masked]>
---
 include/asm-generic/rwonce.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/asm-generic/rwonce.h b/include/asm-generic/rwonce.h
index 92cc2f223cb3..f9dfa88fc04d 100644
--- a/include/asm-generic/rwonce.h
+++ b/include/asm-generic/rwonce.h
@@ -33,7 +33,9 @@
  * atomicity or dependency ordering guarantees. Note that this may result
  * in tears!
  */
+#ifndef __READ_ONCE
 #define __READ_ONCE(x)	(*(const volatile __unqual_scalar_typeof(x) *)&(x))
+#endif
 
 #define __READ_ONCE_SCALAR(x)						\
 ({									\
-- 
2.27.0.212.ge8ba1cc988-goog

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